The proposed project attempts to establish relationships between reproductive behavioral activity and the steroid hormones, estradiol and progesterone, by use of appropriate animal model systems. The biochemical actions of estradiol and progesterone on brain tissues that regulate female sexual behavior will be studied in guinea pigs and rats by use of brain implant techniques, radioactive uptake techniques, cellular fractionation methods and by analysis of cytoplasmic and nuclear concentrations of steroid receptor molecules in brain. Synthetic steroid antagonists (e.g., anti-estrogens) will be used in conjunction with these methodologies as an aid in understanding the neurochemical actions of naturally-occurring hormones. The effects of the naturally-occurring hormones on neurotransmitters, particuarly monoamines, will be studied with the use of brain implants, neurotoxins, transmitter agonists and antagonists, and radioenzymatic assays. The studies will permit a sophisticated molecular analysis of the ways in which hormones act on the brain to influence behavior. The project will also deal with the ways in which behavior can influence biochemical events in an organism. Male guinea pigs and ring doves will be used for this research into psychosomatic influences on reproduction. The methods used will include radioimmunoassay of steroid hormones, particularly testosterone, and radioenzymatic measurement of brain monoamines.